Hold the Raw Sprouts, Please

Lieutenant Commander Rajal Mody, MD, MPH


September 06, 2011

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Hello, I am Dr. Raj Mody. I am an internal medicine and pediatric clinician and infectious disease epidemiologist at the Centers for Disease Control (CDC). I am glad to have the opportunity to talk with you about sprouts, and the risks they pose to health, as part of the CDC Expert Video Commentary Series on Medscape. So-called sproutbreaks have occurred every year in the United States since at least 1995 and have taught us that sprouts are a risky food to eat. Sprouts were found to be the cause of a devastating outbreak of Shiga toxin-producing Escherichia coli infections in Europe this summer. Ultimately, this outbreak caused more than 4000 illnesses, more than 900 cases of hemolytic uremic syndrome, and 50 deaths.

Why are sprouts a risky food, you might ask? Some people think of them as the ultimate healthy food -- fresh and natural. In fact, raw sprouts can be anything but safe. Lessons from outbreaks have taught us that it is a good idea for people who want to lower their risk for foodborne infection to cook raw sprouts or avoid eating them raw.

Here is what we have learned:

Lesson 1: A sprouted seed is a perfect vehicle for pathogens.

A sprouting seed is as inviting and nourishing as Salmonella or E coli could want, and the warm, moist conditions in which sprouts are produced only make matters worse. A single Salmonella organism on the outside of a seed can easily grow to an infectious dose after it has sprouted. The bacteria in or on growing sprouts cannot be washed off. Because Shiga toxin-producing E coli (STEC) have a low infectious dose, sprouts are a great vehicle. Sprouts have also been the vehicle for Listeria, which causes a very dangerous infection for pregnant women and the elderly.

Lesson 2: Sprouts have caused many outbreaks of illness.

Since sprouts were first recognized as a source of foodborne disease in the mid-1990s, they have become one of the "usual suspects" that foodborne disease epidemiologists look for when investigating an E coli or Salmonella outbreak. Since 1998, more than 30 outbreaks have been reported to the CDC, due to many different kinds of sprouts -- alfalfa, bean, clover, and others. In fact, CDC's foodborne disease surveillance systems have identified 3 sprouts-associated outbreaks since June of 2010 that spread across multiple states.

Lesson 3: It is difficult to grow "safe" sprouts.

Once the potential dangers of sprouts became known, the US Food and Drug Administration developed guidance to help sprout growers reduce the risk for pathogen contamination in sprouts they produce and sell. Many sprouts growers have implemented practices to decontaminate seeds before sprouting, but no available method has proved completely effective. People who eat raw sprouts ought to know that they are taking a risk, including people who grow their own sprouts, because the contamination typically starts with the seed.

Lesson 4: Sprouts can make even young and healthy people ill.

This is one of the biggest lessons learned from the outbreak in Europe in 2011 and from our experience with outbreaks in this country. Sproutbreaks in the United States predominantly affect healthy persons aged 20-49 years. A typical victim may be an especially health conscious person in the prime of life. Nevertheless, illnesses from sprouts can be particularly severe in vulnerable populations, such as young children, older adults, pregnant women, and people with compromised immunity.

Lesson 5: It can be hard for those who become ill to remember having eaten sprouts.

We have found in our investigation of outbreaks that were ultimately linked to sprouts that people often do not remember having eaten them, because they are often just a garnish or just one of many ingredients in a food dish. It is not necessary to eat large quantities of sprouts to make a person sick. An ill person's inability to accurately recall what they ate sometimes makes it difficult to pinpoint an outbreak of sprouts.

So what can you do?

  • Clinicians are a trusted source of information. You can relay the message about the dangers of consuming raw or uncooked sprouts, especially to people in the most vulnerable populations -- young children, older adults, pregnant women, and people with compromised immunity. CDC recommends that people in these groups not eat sprouts;

  • If you diagnose a Salmonella, STEC, or Listeria infection, you should report it to your local health department; and

  • If you have a patient with Salmonella or E coli diarrhea or Listeria meningitis, take a food history -- consuming even small amounts of raw or uncooked sprouts could be the source of illness.

I hope you have found this short talk on sproutbreaks informative. For more information, visit the Web resources listed on this page. Thank you for watching.

Web Resources

Food Safety at CDC

CDC Multistate Outbreaks Reports

Suggested Reading

  • Centers for Disease Control and Prevention. Salmonella Serotype Saintpaul infections associated with eating alfalfa sprouts --- United States, 2009. MMWR Morbid Mortal Wkly Rep. 2009;58:1-3.

  • Centers for Disease Control and Prevention. Outbreak of Salmonella serotype Kottbus infections associated with eating alfalfa sprouts --- Arizona, California, Colorado, and New Mexico, February-April 2001. MMWR Morbid Mortal Wkly Rep. 2002;51:7-9.

  • Centers for Disease Control and Prevention. Outbreaks of Escherichia coli O157:H7 infection associated with eating alfalfa sprouts -- Michigan and Virginia, June-July 1997. MMWR Morbid Mortal Wkly Rep. 1997;46:741-744.

  • Mahon BE, Ponka A, Hall WN, et al. An international outbreak of Salmonella Infections caused by alfalfa sprouts grown from contaminated seeds. J Infect Dis. 1997;175:876-882.

  • Brooks JT, Rowe SY, Shillam P, et al. Salmonella typhimurium infections transmitted by chlorine-pretreated clover sprouts seeds. Am J Epidemiol. 2001;154:1020-1028.

Lieutenant Commander Rajal Mody, MD, MPH . Dr. Mody is an officer in the US Public Health Service. He received his MD at the University of California, Los Angeles, and his MPH as well as clinical training in both pediatrics and internal medicine from the University of Minnesota. While training in CDC's Epidemic Intelligence Service, Dr. Mody led investigations of some of the largest foodborne disease outbreaks in the United States. Currently, Dr. Mody works in the Enteric Diseases Epidemiology Branch at the CDC, where he leads many of the agency's surveillance and epidemiologic studies of Shiga toxin-producing E coli infections and the hemolytic-uremic syndrome. Before coming to CDC, Dr. Mody practiced as a primary care physician.


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